#include<iostream>
#include<cstring>
#include<algorithm>

using namespace std;

const int N = 2010;
double a[N];
double sum[25];

int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }
    sort(a, a + n);
    int num = 0;
    int cnt = 0;
    for (int i = 0; i < n; ++i) {
        ++cnt;
        if ( cnt == 100 ) {
            ++num;
            cnt = 0;
        }
        sum[num] += a[i];
    }
    if ( cnt != 0 ) num++;

    double ans = 0;
    double shui = 0.01;
    for (int i = 0; i < num; ++i) {
        ans += sum[i] * shui;
        shui += 0.01;
    }
    printf("%.2f", ans);
    //cout << ans << endl;
    return 0;
}